JP2813137B2 - Thermal conductivity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the thermal conductivity of a thin plate, for example, a flat diamond plate, or an object such as a film.

[0002]

2. Description of the Prior Art In the case of a steady-state heat flow in one direction flowing through a sample to be measured, the thermal conductivity K
Is given by the following equation. K = P / A (ΔT / Δx) (1) Here, P is a heat flow per unit time along the X axis penetrating the longitudinal section of the sample, and the section of the sample is a plane parallel to the YZ plane. , And its area is A. And ΔT is
This is the temperature difference along the distance Δx. This Δx is measured by attaching a pair of temperature sensors made of thermocouples (thermocouples) separated by a distance Δx in the X direction to the object to be measured. The technology that measures this one-way heat flow is
“ElementaryPhysics: Classical and Modern” (197
5th year) Richard T. Weidner and Robert L. Sells,
On pages 306-307.

In this technique, a rod-shaped sample having a uniform cross section A and a pair of end surfaces is surrounded by an insulating material to minimize heat exchange with the sample through the side surface. I have to. One end of the sample is maintained at a constant high temperature T _h, and the other end is maintained at a constant low temperature T _c. In the steady state, the heat flowing through the cross section of the rod per unit time has P given by equation (1), and its temperature gradient ΔT / Δx is independent of the X axis, anywhere along the rod, anywhere along the rod. They have the same value.

In the prior art, performing this kind of one-dimensional temperature measurement is complex and time consuming, because each time a different measurement is taken, a hot bath and heat transfer This is because the pair must be attached to the sample. Then, in order to perform accurate measurement, it is necessary to carefully measure over a long time. In addition, the required thermal insulation is finer and more fragile at the thermocouple and its wiring, and also at the heat source and its wiring, and tends to buckle and collapse due to the required insulating material. There is.

Next, in the case of a disk-shaped heat flow P in the radial direction, the thermal conductivity K in a steady state is given by the following equation. K = {P / (R2 / R1)} / {2πh (T2-T1)} (2) Here, T1 and T2 are the distances R1 in the radial direction from the point of the sample arranged at the center on the disk. At the temperature measured at R2, h is the thickness of the sample measured parallel to the Z-axis direction (that is, perpendicular to the XY plane), and it is assumed that a heat flow P in the radial direction is generated. For example, the sample is a disk K having a pair of end surfaces separated by a distance h.
In the prior art, due to radiation and other heat loss problems, h is set to be much larger than R2 (at least ten times or more) so that the heat flow only flows in the radial direction. . Thus, the heat flow flows only in the radial direction, and K is determined by equation (2). However, to minimize errors due to edge effects, the temperatures T1 and T2 need to be measured at points inside the sample (ie, points in the sample). This makes the measurement complicated and time-consuming.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object to be measured according to the present invention is a relatively thin plate or plate having a thickness h. I can't meet the restrictions on Therefore, accurately measuring the thermal conductivity of an object to be measured, such as a plane, cannot be achieved using conventional thick radial heat flow measurement techniques. Therefore, the object of the present invention is to
An object of the present invention is to provide an apparatus and a method for accurately measuring the thermal conductivity of a thin plate-like film, plate, plate or the like.

[0007]

In order to solve the above problems, an apparatus according to the present invention is as described in the appended claims.

[0008] The plastic sheet used in the present invention is bonded to a heat sink, thereby maintaining the plastic sheet in a mechanically tensioned state (tensed state). Also, the first temperature sensor and the second temperature sensor form a differential thermocouple, and connection wires to the first temperature sensor and the second temperature sensor are bonded to a plastic sheet. The apparatus of the present invention provides a fifth position (between the first position and the second position) of the plastic sheet.
And a third temperature sensor disposed at This third temperature sensor has an access wire bonded to the plastic sheet. The heat source has a resistor bonded to the plastic sheet and an access wire bonded to the plastic sheet.

[0009]

1, 2 and 3, a thermal conductivity measuring device 10 for measuring the thermal conductivity of a sample (measurement object) 60 is shown.
0 has a heat sink 1 made of copper. The heat sink 1 has four measuring walls 59, 69, 79 surrounding the opening,
It is a square base with 89. Each wall is about 1-2c
The opening in the heat sink 1 is filled with a heat-insulating filler 61 made of foamed rubber.

The thin plastic sheet 2 (made by Kapton)
Joined to the upper surfaces of the measuring walls 59, 69, 89, the thin plastic sheet 2 is mechanically pulled and tensioned, that is, the thin plastic sheet 2 is arranged so as not to hang down, Joined. This thin plastic sheet 2 has a thickness of about 8 μm,
The thin plastic sheet 2 having a thickness of 8 μm and a size of 4 cm × 4 cm is in contact with the upper surface of the heat-insulating filler 61 and is disposed thereon.

An auxiliary heat conducting plate 3 is arranged on the left part of the thin plastic sheet 2 (FIG. 3) and is fixed firmly on a part of the upper surface of the measuring wall 79 of the heat sink 1 (FIG. 3). The clamp bar 4 and the upper surface of the measuring wall 79 are firmly clamped by means such as brass screws 5, 6, 7) to form good thermal contact with the heat sink 1.

The auxiliary heat conducting plate 3 is generally made of copper,
Its thickness is about 0.1mm, 0.5cm × 1.0cm
Is a square. The bottom of the auxiliary heat conductive plate 3 is formed by a thermocouple formed by the fine wires 28, 29, 30.
If arranged below the auxiliary heat conducting plate 3, its bottom is coated with an electrically insulating layer 8 (FIG. 3).

The connecting posts 11, 12, 13,..., 1
, 38 are generally made of copper and insulated cement (epoxy) and embedded in holes in the upper surfaces of the opposing measuring walls 69, 89, and the connecting posts are removed from the heat sink 1. It is electrically insulated and mutually insulated. Each fine line 21, 22, 23, 25, 26,
27, 28, 39, 41, 42, 43, 44, 45, 4
6, 47, 48 are individually connected to each one of these coupling posts as shown in FIGS.
These fine wires are bonded to the upper surface of the thin plastic sheet 2 by epoxy cement to form a mechanically stable wire array placed on the heat insulating filler 61. Each of the fine wires 21, 22, 41, 42 is a copper or gold wire having a diameter of about 25 μm, so that the amount of heat conduction by this wire is negligible.

A resistor (51) is adhered to the upper surface of the thin plastic sheet 2 by epoxy cement, and one end of each of the thin wires 21 and 22 is electrically connected to the other end of each of the thin wires 41 and 42.

Next, a method for measuring the thermal conductivity using the apparatus of the present invention will be described. When the sample (device under test) 60 is arranged and a voltage is applied, a current i flows from the coupling post 11 to the coupling post 31 via the fine wires 21 and 41 and the resistor 51. Fine wires 22 and 42 connected to each end of resistor 51
The purpose of is to provide a zero current wire and to accurately measure the voltage across resistor 51 relative to this voltage required for the calculation of P in equation (1).

The thin wires 23, 24, 25 are
4 form a differential thermocouple with the thermocouple formed by the thermocouple 4, and the thin wires 43, 44 form a single thermocouple at the junction 53. Thin lines 23 and 25 are chromel or constantan, respectively, and thin lines 24
Is constantan or chromel, and its diameter is about 50 μm. As is known in the art, the voltage ΔV applied to the coupling posts 13 and 14 is proportional to the temperature difference ΔT between the junctions 52 and 53, and ΔT / Δx required in the equation (1).
Can be determined by measuring the distance Δx between the values of the joints 52 and 53.

The thin wires 43 and 44 form the junction 53 of the thermocouple. One of these wires is chromel and the other is constantan, which allows the binding post 33,
The voltage V applied to the heat sink 34 is proportional to the absolute temperature at the junction 53, and the thin wires 33 and 34 have the same absolute temperature as the known temperature of the heat sink 1. The joint 53 is formed of the joint 5
2, 54, located approximately in the center of the coupling posts 13, 14,
Is calibrated, and this voltage ΔV can be converted into a desired temperature difference ΔT.

The distance between the resistor 51 and the joint 52 is
At least 10 times the thickness of the sample (device under test) 60, the directional distribution of the heat flow flowing through the sample (device under test) 60 is in the X direction (from the sample (device under test) 60 to the auxiliary heat transfer plate 3). Independent of the position along the direction, it is arranged near or in the region of the joints 52, 53, 54. The left part of the sample (measured object) 60 and the thin line 3
The connection to zero is such that the local thermal conductance is uniform over the width of the sample (the length of the sample in the X direction is much larger than the width and its thickness). ).

The resistor 55 has thin wires 26, 27, 45, 4
6 and the thin wires 26, 27, 35, and 36 have been added in order to perform calibration due to loss due to heat conduction or radiation from the surface of the sample (measured object) 60. In this regard, JEGraebner and JAHerb
Co-author, `` Dominance of Intrinsic Phonon Scattering
in CVD Diamond ”(1992 Diamond Films and T
echnology) 1st volume No. 3, pages 155-164 and 157-158. In addition, another differential thermocouple formed by the thin wires 28 and 29 and between the thin wires 29 and 30 is added, and further, another thermocouple formed by the thin wires 47 and 48 is used to assist. Heat conduction plate 3
To check the thermal bonding between the heat sink (1) and the auxiliary thermal conductive plate 3 and the sample (measured object) 60.

The sample (measurement object) 60 is rectangular and has a much smaller uniform thickness than its width and length. The sample (measured object) 60 does not necessarily have to be square, but has a width on the right side (Y direction).
Is approximately equal to the length of the resistor 51 (= Y direction), the width on the left side is approximately equal to the width of the auxiliary heat conductive plate 3, and the width (Y direction) of the sample (measurement object) 60 is Any material can be used as long as it is uniform in the region between the portion 52 and the joining portion 54 and can secure the heat flow in the position direction between the joining portion 52 and the joining portion 54. The thermal conductivity measuring apparatus 100 of the present invention is suitable for measuring the thermal conductivity (XY plane) of the surface of a sample (object to be measured) 60.

The purpose of the thin plastic sheet 2 is to make the resistor 51 and the joints 52, 53, 54 and the thin wires 21, 22, 2,
3, 24, 25, 41, 42, 43, 44 together with a mechanically stable support system. Thermocouple joints such as joints 52, 53, 54 are all formed by spot welding with an arc or lead tin solder in a flux containing the auxiliary heat conducting plate 3.

Next, a method for measuring the thermal conductivity of the surface of the sample (measured object) 60 will be described. The sample (measurement object) 60 is arranged such that the left end is on the auxiliary heat conductive plate 3 and the right end is on the screw 5. After arranging the sample (measured object) 60 in this way, the heat insulating medium 62 (styrene foam) is mixed with the sample (measured object) 60.
And the remaining (exposed) top surface portion of the thin plastic sheet 2 and the top surface portion of the auxiliary heat conducting plate 3. The compressive force generated by the metal weight 63 pushes the insulating medium 62 downward, reducing the distance between the bottom of the insulating medium 62, the exposed upper surface portion of the thin plastic sheet 2 and the auxiliary heat conducting plate 3. . In this way, the heat loss is reduced and the sample (measured object)
Good thermal contact between 60, the heating device, the thermocouple joint and the auxiliary heat conducting plate 3 is obtained.

The operation of measuring the thermal conductivity on the surface of the sample (measured object) 60 will be described below. The resistor 51 functions as a heating device by flowing a current i therethrough by a current source (not shown) connected to the coupling posts 11 and 31. After the steady state has been obtained, the value of P in equation (1) becomes equal to P = νi. Where ν is the voltage difference across resistor 51, which is measured between coupling post 12 and coupling post 32, and i is the current flowing through resistor 51 through coupling post 11 and coupling post 31. Value. The above equation P = νi is effective under the condition that all of the heat (excluding other heat) generated by the resistor 51 enters the sample (device under test) 60 and the sample (device under test) 60 This is the case when only the heat that comes out reaches the region arranged on the left side of the joint 54. These conditions are satisfied by the thermal insulation formed by the heat-insulating filler 61 and the heat-insulating medium 62, and the sample (measured object)
This is the case where the width (Y direction) of 60 is much smaller than both the width of the heat insulating filler 61 and the width of the heat insulating medium 62.

P = νi can be calculated from the measured values of ν and i, and the value of ΔT / Δx can be determined from the measured value of the voltage of the thermocouple.
Is measured by a known technique. Thus, the value of the surface thermal conductivity of the sample (object to be measured) 60 in the X direction is calculated by the equation (1).
And the measured value of ΔT and the value of K calculated from equation (1) can be determined after they no longer fluctuate with time. Using the thermal conductivity measuring apparatus 100 of the present invention, the surface thermal conductivity in the X direction of different samples, after measuring the thermal conductivity of each sample, just remove the metal weight 63 and the insulating medium 62, then It can be measured by placing the next sample there.

FIG. 4 shows a thermal conductivity measuring device 300 used for measuring the thermal conductivity of a sample having a deformed outer shape. The components shown in FIG. 4 are equivalent to those obtained by adding 100 to the component numbers shown in FIGS. 1 and 3, and have the same structure and function. The opening of the heat sink 101 is filled with a filler (not shown) similar to the heat-insulating filler 61. A major difference between FIG. 4 and FIGS. 1, 2 and 3 is that the heating device (resistance) 151 is not linear but annular.
The auxiliary heat conduction plate 3 (FIGS. 1, 2, and 3) is a point that becomes the pedestal 103 (FIG. 4).

Wires 121, 122, 141, 144
Is connected to the top surface of the plastic sheet 102 with epoxy cement, and likewise wires 123, 124,
125 is bonded to the bottom surface of the plastic sheet 102, and wires 128, 130, 147, 148 are bonded to the surface of the pedestal 103. In measuring the thermal conductivity, a sample body (not shown) is placed on a heating device (resistance) 151, which covers all its points and extends beyond those points, Annular target heating is achieved. Thermal conductivity measuring device 30
In operation at 0, an insulating medium similar to the insulating medium 62 is placed over the sample, and a metal weight 63 is placed over this insulating medium. The thermal conductivity in the plane (XY) direction is calculated by the equation (2).

Before placing the sample on the thermal conductivity measuring device 100 or the thermal conductivity measuring device 300, the heat conductive grease is applied to the lower side of the thermal conductivity measuring device 100 or the thermal conductivity measuring device 300. To improve the bonding of the sample to the thermocouple, and the resistance and thermal contact between the auxiliary heat-conducting plate 3 or the pedestal 103. It is preferable that the thermal conductivity measuring device 100 or the thermal conductivity measuring device 300 is arranged and operated in a vacuum chamber (1 Pa or less).

As a modification of the present invention, the wires 21 and 2
2, ..., 30; 41, 42, ..., 121, 12
2, 123, 124, 125, 141, 142, 144
By depositing the resistors 51, 55 and 151 as thin film wires and thin film resistors, it can be realized on the plastic sheets 2 and 102.

[0029]

As described above, according to the apparatus of the present invention, it is possible to accurately and easily measure the thermal conductivity of a film.

[Brief description of the drawings]

FIG. 1 is a perspective view of an apparatus for measuring the thermal conductivity of a square sample (device to be measured) according to one embodiment of the present invention.

FIG. 2 is a partially enlarged view of the apparatus shown in FIG.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1 showing a state in which a sample (device to be measured) is arranged in the device in FIG. 1;

FIG. 4 is a partial cross-sectional perspective view of an apparatus for measuring the thermal conductivity of a flat plate according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 100 Thermal conductivity measuring apparatus 1 Heat sink 2 Thin plastic sheet 3 Auxiliary heat conductive plate 4 Clamp bar 5, 6, 7 Screw 8 Electrical insulating layer 11, 12, 13, ..., 18 Coupling post 21, 22, 23, 24 Thin wires 25, 26, 27, ..., 30 Thin wires 31, 32, 33, ..., 38 Coupling posts 41, 42, 43, ..., 48 Fine wires 51 Resistors 52, 53, 54 Joints 55 Resistor 59, 69, 79, 89 Side wall 60 Sample (device to be measured) 61 Insulation filler 62 Insulation medium 63 Metal weight 101 Heat sink 102 Plastic sheet 103 Pedestal 104 Clamp bar 105, 106, 107 Screw 121, 122, 123, 124, 125 wires 128, 129, 130 wires 141, 142, 143, 1 4 wire 147 wire 151 heater (resistance) 152, 153, 154 junction 159,179 sidewall 300 thermal conductivity measuring device

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 25/18

Claims (5)

(57) [Claims] 1. A heat sink body having an opening (1)
B) a heat insulator (61) that fills the opening; c) a sheet (2) disposed at an exposed portion of the heat insulator; d) a first spaced apart position (52) of the sheet and a second. The first temperature sensors (2
3) a second temperature sensor (25); e) a heat source (51) located at a third position on the sheet.
F) an auxiliary heat transfer plate (3) having a first end disposed on the heat sink body (1) and a second end disposed on a fourth position of the sheet; The thermal conductivity measurement device according to claim 1, wherein the first position and the second position of the sheet are between the third position and the fourth position. 2. The sheet according to claim 1, wherein the sheet is a plastic sheet adhered to the heat sink body, and the plastic sheet is held in a tensioned state.
Equipment. 3. The method according to claim 1, wherein the first temperature sensor and the second temperature sensor form a differential thermocouple, and an access wire of the first temperature sensor and the second temperature sensor is connected to the sheet. The apparatus of claim 1, wherein 4. The apparatus according to claim 1, wherein the heat source comprises a resistor connected to the sheet, and the access wire is connected to the sheet. 5. The first position (52) and the second position (5).
Device according to claim 1, further comprising a third temperature sensor (43, 44) arranged in a fifth position (53) during 4).